In the past, it has been known to dip-form a dip-forming composition which contains a natural latex such as a latex of natural rubber to obtain a dip-formed article used in contact with the human body such as a nipple, balloon, glove, medical balloon, and sack. However, a latex of natural rubber contains proteins which cause allergic reactions in the human body, so sometimes there was a problem as a dip-formed article which directly contacts the mucous membrane or organs of the body. Therefore, studies have been made on the use of a latex of a synthetic nitrile rubber.
For example, Patent Document 1 discloses a latex composition containing a carboxyl group-containing conjugated diene-based rubber latex and an amphoteric surfactant comprised of a weak base and strong acid and a dip-formed article obtained by dip-forming this latex composition. Further, the above Patent Document 1 discloses the art of using a sodium hypochlorite aqueous solution to treat the surface of the obtained dip-formed article. The surface treatment using such a sodium hypochlorite aqueous solution is usually performed so as to improve the put-on and strip-off ability of the dip-formed article, but on the other hand, when using a sodium hypochlorite aqueous solution for surface treatment as in the above Patent Document 1, chlorine ends up penetrating to the inside of the dip-formed article, so chlorine addition reaction ends up being occurred not only at the outer surface, but also up to the inside and therefore there was the problem that the tensile strength ended up falling.